During 1852 he gave organ recitals in Saint Vincent de Paul, La Madeleine and Saint Eustache churches in Paris, where he stunned audiences with his technique. Particularly notable was his brilliant pedal-playing, which owed a good deal to his studies of Bach's music (at the time Bach's organ works were not at all well known in France). In 1857 he married the EnglishsopranoHelen Sherrington (1834–1906), who in the following decade emerged as a leading English concert and operatic singer. He died at Zemst, near Mechelen, Belgium.

At the request of the Belgian clerical authorities, Lemmens returned to Belgium to found a school for Church music in Mechelen in 1879. This was to become the future Lemmensinstituut after its move to Leuven in 1968. Lemmens could only work at the development of this school for two years, as he died on 30 January 1881. He was succeeded by Edgar Tinel.